Thursday, 10 November 2016

I always wanted to experiment with this design to feed my horizontal loop. Since the system works with a simple transformer the radio is not physically connected with the antenna and that's one of the things I like of this design. Other advantages claimed are better balance compared to a T-Match with 1:4 balun and a higher antennacurrent into the antenna. So, I aquired a homemade matcher from PA1PRD Erik at a sale from our radioclub. It is a very simple endfed tuner which he used for a 80/40m wire hanging in the air below a kite. Both coil and capacitor are homemade. Just perfect for my little project. I dismantled the whole thing and made some improvements on the capacitor.

Measuring everything I was already afraid I would have too less capacity (140pF), but for just a experiment it's not a problem. I don't bother you all with the technical aspects of building this whole antennatuner but in the end it cost me a "few" hours. What was more important to me were the results. I wanted to verify the claims given. At first I measured the current behind my Palstar AT2K which is a T-match with built in 1:4 balun. Transmitting with 40W FM I measured about 0,8A on one side and 3,4A on the other side of the open line with my clamp meter.

Switched back to my vertical and had a lot of signals from stations all over the band. So I thought I made a fault constructing the antennatuner. Then suddenly it occured to me that I connected the wrong ladderline (have 2 coming into the shack remember). I was matching a piece of about a meter ladderline and the tuner could still get a 50Ohm match!!! Wow!. Now, I connected the right ladderline which connected the loop to the tuner. But the disaster already happened. I probabely forgot to switch off the MFJ-259B and the high radiation from the unshielded tuner and high antennacurrents probabely fried the very sensitive diodes inside. Stupid me!

Unfortenately I damaged my MFJ-259B analyzer during the experiment and so I searched on internet how to repair the thing. That didn't look easy to me as the diodes are SMD types. Thinking about my escapades repairing the IC-706 and modifying the FT-817 I decided to find someone that repairs these things. I found radioamateurshop.nl which is not really a shop although it is in the name. It is a repairservice for hamradio equipment. So I already shipped the analyzer and hope it will be repaired soon.

I just tested it to see if it worked. Till now no contacts were made. I probabely will try that another time. The design and construction are very simple. Wish I knew this before I bought that expensive Palstar 10 years ago. I imagine what I will know in the future ;-). 73, Bas